When gas discharge lamps, e.g. xenon lamps, are used especially in the automotive field and also in other fields of use in which the discharge lamp control electronics has to meet increased requirements, which is the case e.g. in the field of use for mobile devices, high demands on the electric strength and reliability have to be satisfied on the one hand, while compact dimensions are also necessary on the other hand. In addition, the electronic components, including the ignition transformer, required for operating discharge lamps and in particular for igniting these discharge lamps should be mountable in an economy-priced and reliable manner, and also the mechanical fixing of the electronic components, e.g. of the ignition transformer, is of great importance in this context.
Especially for igniting a discharge lamp, comparatively high voltages in the range of a few 10 kilovolts (kV), e.g. of approx. 30 kV, are required, as is generally known, so as to initiate a reliable ignition of the gas mixture in the discharge chamber of the respective lamp, which is often also referred to as arc tube. The necessary high ignition voltage is normally generated by means of an ignition transformer, which has supplied thereto a comparatively low primary voltage of approximately a few hundred volts from an associated electronic ballast and which then transforms this primary voltage to the high ignition voltage. If the dimensions of respective functional groups, e.g. of the ballast and of the ignition unit, are reduced, it will therefore be necessary to provide also the ignition transformer in a suitable configuration, e.g. with respect to the geometrical and magnetic nature of the core material and the provision of the primary winding and of the secondary winding, so as to produce the necessary high ignition voltage on the one hand and so as to guarantee nevertheless the necessary high electric strength on the other. To this end, it is necessary to provide sufficiently large insulation tracks, in particular in the area of the ignition transformer, and also in the area of other electronic components so as to guarantee a reliable functioning of the ignition system under demanding ambient conditions, as is e.g. the case when the ignition system is used in the automotive field, where the respective electronic components have to be operated over a large temperature range and under respective environmental influences, such as snow, rain, moisture, mechanical vibration loads and the like, in an environment with high disturbance wave emission. During assembly of an ignition module, the electronic components and the ignition transformer therefore have to be arranged on one or on a plurality of suitable component part carriers in such a way that the mechanical reliability and therefore also the reliability of the respective electric connections remains observed under these demanding conditions and that also the necessary electric strength is guaranteed between the various electric connections at different potentials. To this end, suitable plastic materials are often provided in the vicinity of the critical components of the component part carrier, whereby suitable insulation tracks are obtained. For example, attempts are often made to provide adequate “labyrinths” of plastic walls at least in the finished, mounted condition of an ignition module so that e.g. critical areas, such as the high-voltage connection of the ignition transformer as well as the connection region of the discharge lamp, are surrounded by voltage-resistant plastic material. These areas must, however, be easily accessible during assembly of the ignition module so that a reliable electric connection can be established, e.g. by welding or soldering. For example, known ignition modules include a component part carrier with a plurality of components, said components interengaging during final assembly such that the desired plastic insulation tracks are established in the critical high-voltage areas.
In addition, for obtaining the necessary mechanical and electrical reliability of the ignition transformer, the latter is, normally after having been fixed to the component part carrier and after having been electrically connected, encompassed with potting material. One of the components of the component part carrier comprises, for example, a suitable chamber into which the ignition transformer is inserted, then connected and finally potted. During potting of the ignition transformer, it is very important for an increased reliability that the respective potting chamber is filled without any cavities being formed, so as to guarantee the mechanical properties as well as the electric properties even under demanding environmental conditions. During the assembly of the ignition transformer and in particular during the formation of the electric connection to a high-voltage conducting track, which, in turn, establishes a connection to the discharge lamp, welding methods making e.g. use of a laser, or soldering methods making use of suitable flux materials, are normally carried out. In so doing, smoke residues may be formed, especially during welding processes, said smoke residues depositing on the adjacent walls of the potting chamber, thus having a negative influence on the adhesion of the potting material during the subsequent potting of the potting chamber, and/or contaminating the potting material directly, which will then also lead to an impairment of the electric strength. This unsatisfactory adhesion of the potting material results in a reduced reliability with respect to mechanical loads, e.g. vibration loads, and especially with respect to the electric strength of the whole setup. In a similar way, also the use of a flux material for a soldering process leads to a contamination of the adjacent potting chamber walls, and this may again lead to an impaired adhesion of the potting material during the subsequent process. The problem of an insufficient adhesion of the potting material becomes even more prominent, when the dimensions of a respective ignition module are to be reduced, since also the dimensions of the respective potting chamber normally have to be reduced in this case. This results, on the one hand, in an increase in the total demands on the ultimately necessary electric strength, and, on the other hand, it may also lead to a stronger contamination of the potting chamber walls.
Especially for a further miniaturization of respective ignition modules, which are used e.g. for headlights in vehicles and also for other applications, it is therefore normally necessary to use, in addition to a suitable arrangement and fixing of the electrical components of the ignition module for observing the necessary electric strength, possibly also complicated methods for decontaminating the potting chamber walls, and this, in turn, leads to a very complicated manufacturing process during production of the ignition module. If further electrical components should be integrated, which are required e.g. for controlling the operation of the gas discharge lamp prior to, during and after the ignition, even higher demands have to be fulfilled in the case of the desired compact structural design, in particular in the automotive field, since also thermal aspects have to be taken into account in addition to the electric strength and the interference resistance, i.e. the thermal losses which occur when respective circuit groups are operated and which are caused e.g. by voltage transformers and the like, in combination with the heat transmitted to the lamp socket through the discharge lamp, lead to locally high temperatures, and this had normally the effect that the ignition module in combination with the lamp socket on the one hand and the additional electronic components in the form of a ballast were configured as separate units, which, via a cable connection, are arranged in spaced relationship with one another. Although this reduces the problems entailed by the electromagnetic disturbance of the individual circuit areas as well as the thermal characteristics of the spatially separated circuit areas, a much higher expenditure is necessary with respect to the overall material cost as well as the assembly of the discharge lamp and the associated control electronics, since two housings as well as adequate connection elements are required.